Its
generally observed that more than 90% of the construction of residences,
commercial buildings and Industries at the small scale level are done directly
by the Owner with the help of Labour Contractor and a Architect / Engineer.
Here we try to list the activities to be undertaken by the Civil Labour
Contractors, the work involved and precautions to be taken during construction
since the Owner is dierectly incharge here. This article shall be periodically
reviewed and additions made periodically.

Basement

CONSTRUCTION
ACTIVITIES UNDERTAKEN FROM FOUNDATION TO RCC ROOF:

The
Contractor shall Mark the Layout of Building on the Ground in the form
of centre lines of walls and coloumns. These centre lines shall by guided
by brick bhurjis made along the centre line at a distance of 4' from the
outer walls and coloumns with the centre marked on the bhurjis woth fresh
plaster. Excavation to be done to the prescribed basement floor lvl at
the cost of the owner. Balance excavation to be done at contractors cost
after remarking the position of coloumns on excavated ground and also
making temporary markings of centre lines on excavated sides.Marking the
foundation/ beams sizes and then doing the balance excavation giving shape
to the raft foundation / coloumn foundations.

Laying
of Plain Cement Concrete as per Architects directions to the required thickness.

In case external waterproofing is to be done the its to be done on the PCC
if internal the that shall be done after completing the RCC of thr basement.
Now Contractor is to do the final Layout of walls, coloumns and beams on
the PCC and get it verified by the architect / engineer for accuracy.

Contractor
is to guide the bar binders ( Lohar) with respect to laying of steel in
foundations and has to position the coloumn reinforcement. Payment to bar
binders to be done by owner usually around Rs 1/- per Kg. Cover blocks to
be made by contractor in PCC at the time of laying PCC in the thicknesses
stipulated and placed below or around reinforcement so as to provide proper
cover. After laying of the Steel reinforcement it is to be checked by the
Architect for accuracy and cover to reinforcement

Contractor
is to make provisions for shuttering material required to give shape to
the foundation elements and to position it at his cost.

Contractor
is to pour concrete of prescribed mix in foundation which is usually M 150
ie ( 1: 2: 4) - ( 1 cement : 2 coarse sand : 4 coarse aggregate) by volume
or M 200 ie.( 1: 1.5: 3) in small residential projects. In case of bigger
projects the mix is designed for giving the required strength stipulated
by the structural designer. It has been observed that owners instead of
using Cement of grade 43 use cement of grade 53 in RCC on the behest of
suppliers and in their belief that this will be more strong, this should
not be done since cement of grade 53 sets very early and also has more shrinkage
which can cause surface cracks to appear with in a few hours of laying if
not cured with water. Its also observed that the time lapse between mixing,
laying, vibrating the concrete and then smoothing it to shape / level required
in normal circumstances is at certain points of time more than the setting
time of Grade 53 Cement. Thus Cement of grade 43 should be used for concreting
unless other grades are specified by the architect / structural designer.
Additives to cement may be added on advice.

Contractor
is to do shuttering of Coloumns and RCC walls as per details provided
by architect in conjunction with the steel binder and ensure positioning
of spacers to provide proper cover to reinforcement. Care should be taken
by him to ensure that the shuttering is tight so that it does not bulge
at time of concreting and that the wall does not go out of plumb. The
architect / engineer should be requested to check the accuracy of shuttering
and whether its in plumb ie: ( Its exactly vertical and not bending outwards
or inwards.)

Contractor
is to pour concrete as per mix adviced in walls and coloumns and is to vibrate
it properly for ensuring proper laying, cement additives can be added for
generating proper flow and compaction of concrete as per advice of architect.
Casting of walls is generally done in two lifts causing a joint to be formed.
Care should be taken to provide a water key at this point. For this at the
time of laying the lower wall a depression of aproximately 1" x 1"
x 1" with any wooden batton or plank should be made in centre of the
top of RCC wall. When concrete is layed in the upper half it fills in to
this groove forming a water seal and reducing chances of seepage from joint.
This precaution should also be taken at the time of laying of foundation
and groove should be provided along the centre line of RCC wall position.

Contractor
is to cast the balance height of coloumn after proper shuttering upto roof
beam bottom.

During
all the above activities of concreting right from the foundation to roof
and above its generally seen that the masons at times are careless in keeping
the reinforcement of coloumn vertical or in plumb or in providing proper
cover to it thus causing it to drift to one side due to its own weight and
shifting from the centre line by an inch or more. This aspect should be
specially checked by contracter, owner and architect at every stage and
where its height above the shuttering is more and its swaying due to its
own weight it should be tied in various directions to keep it in plumb.

Contracter
is to provide and do shuttering of the roof as per structural drawings and
check its level. He has to ensure that proper amount of supports are provided
and also that the shuttering is not uneven or done with very old planks
or bent plates. Since generally the shuttering is taken on rent by the contractor
he does not provide shuttering of wareproofply or of steel sections made
to the size required since this increases the cost per sqft. But steel shuttering
of various coloumn sizes is generally available for rent and also steel
plates for roof shuttering are also available for rent and these should
be used. Architect / engineer should check the shuttering for levels and
design aspect he should also check the supports for any loose ends.

Contractor
should guide the steel binder w.r.t laying of steel reinforcement in roof
and his masons should provide the proper cover blocks where required. Overhere
its generally seen that at the time of positioning of beem main bars at
the junction with coloumn they passed from outside of one side if vertical
coloumn reinforcement by the binder this causes it to either press the coloumn
bars inwards thus disturbing there plumb in the evertical or reducing finishing
the cover to the beam bars since they are pushed outwards by the coloumn
bars this also at times causes the shuttering to bulge or reduced space
blocks proper flow of concrete in to positon required. This can be avoided
by gently bending the beam bars inwards before the junction causing them
to pass on the inside of the coloumn reinforcement without causing any of
the above problems.

Its
also seen at times that some architects / engineers do not provide the distaces
of curtailment of bars or the distance for which cranked bars are to travel
into the next slab or the distance from edge of beam from which bars are
to be cranked by simply giving a general rule or leaving it to the knowledge
of the steel binder. This practice should be avoided since the binder is
not a engineer and very few working in the general residential sector are
educated enough do make percentage calculations thus all distances should
be mentioned by architect / engineers in there drawings and shourtcuts should
be avoided. This should be looked into by the owners and he should request
them to provide detailed drawings.

Time
should be given to the electrical contractor and the plumbing contractor
for laying there pipes, fan and light boxes properly. Thus a gap of one
day should be provided after the binding of steel reinforcement so that
both the electrical and sanitory contractors can execute there work properly
and also for the architect / engineer to check the reinforcement, shuttering,
electrical and sanitory work. This at itmes is avoided by the contracter
thus forcing the electrical and sanitory person to do work on the morning
of pouring of concrete and the engineer to check incomplete reinforcement
which is an unsafe practice. Thus while finalizing the contracter make this
as one of the conditions that one day gap shall be given after laying of
reinforcement.

Contractor
has to lay the concrete in roof slab as per specified mix and design. Care
should be taken to provide the specified thickness of slab concrete and
also to vibrate it properly so as to remove air gaps and make concrete fill
into all edges. Masons have the tendency of adding water to the layed concrete
to make it flow in the beams this should be avoided and be done in rare
occasions where some time has elapsed and the concrete is dry otherwise
it drains out the cement and the sand through gaps in shuttering reducing
strength. Again here in small works its observed that the labour doing the
mixing of concrete is not so carefull in ensuring the proper mix thus owner
should depute one of his own persons to keep a check at the point of mixing
for volumes of cement, coarse sand, coarse aggregate. The labour and the
mason also have the habit of increasing the quantum of coarse sand for getting
easy workability this causes reduction in strength of laid mix and less
consumption of cement. We advice that today we have many additives for concrete
available in the market for reasonable price for increasing the workability
of concrete and these should be used instead of disturbing the mix ratio.
Adding too much of water by labour for getting smooth flow of Concrete should
also be avoided.